I need a quick answer on this test.
1 answer:
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Answer:
see explanation
Step-by-step explanation:
(3)
Given cosΘ = -
Then by Pythagoras' theorem the third side is 3 ( 3,4, 5 triangle )
Since Θ in second quadrant then sinΘ > 0
sinΘ =
Using the trigonometric identity
sin2Θ = 2sinΘcosΘ, then
sin2Θ = 2 × × -
= -
(4)
Using the trigonometric identity
cos(x - y) = cosxcosy + sinxsiny
note cos15° = cos(45 - 30)°
cos(45 - 30) = cos45cos30 + sin45sin30
= ( ×
) + (
×
)
=
